The invention relates to anionic polymerization resulting in very high molecular weight, highly branched diene polymers. More particularly, the invention relates to novel multiply-metalated, solid supported anionic polymerization initiators that are useful for producing such polymers. The macro-branched polymers synthesized by the process of the invention exhibit desirable properties, such as the ability to absorb hydrocarbon solvents and oils, and are readily compounded to form vulcanizable elastomeric compounds and articles that have excellent resistance to wear and tear and exhibit reduced hysteresis properties.
When producing polymers for use in rubber articles, such as tires, power belts, and the like, it is desirable that these polymers are easily processible during compounding and have a high molecular weight with a controlled molecular weight distribution, glass transition temperature (T.sub.g) and vinyl content. It is also desirable that reinforcing fillers, such as carbon black, be well dispersed throughout the rubber in order to improve various physical properties. This dispersion can be achieved, for example, by end capping polydienes by reacting a metal terminated polydiene with an end capping agent, or by utilizing functionalized anionic polymerization initiators such as lithium-based amine or amide initiators that incorporate a functional group onto one or both ends of the polymer chain. Rubber articles produced from vulcanized elastomers exhibiting these properties, will have reduced hysteresis resulting in an increase in rebound, a decrease in rolling resistance and less heat build-up when mechanical stresses are applied.
Anionic polymerization initiators based on lithium are well known for producing linear polydiene homopolymers and copolymers. Lithium-based macrocyclic anionic polymerization initiators have also been described in U.S. Pat. Nos. 5,677,399 and 5,700,888. These initiators are utilized to form stable macrocyclic polymers that have low viscosities at high molecular weights and thus provide for enhanced polymer processibility during molding, extruding and the forming of films. Such polymers can be compounded to form vulcanizable elastomeric compounds and articles that exhibit reduced hysteresis properties.
There is still a need, however, for anionic polymerization initiators that can be used to synthesize high molecular weight linear polymers that are easily processible and have the desirable properties described above.